This is a replication with a middle class sample of 49 infants of a study previously carried out with a sample composed largely of lower socioeconomic infants and families. Data on environmental variables are obtained through time-sampling observations in the homes. Measures of infant development are obtained from the Bayley Scales and through a structured test designed to measure exploratory behavior and preference for novel stimuli. In the earlier study significant relationships were found between specific environmental variables and specific aspects of infant development at 6 months. For example, kinesthetic stimulation by the mother was significantly related to the Bayley Mental Development Index and to measures of Goal Directedness, Object Permanence and Social Responsiveness. We are replicating this study in order to determine whether similar relationship will hold in patterning of stimulation. Preliminary analyses indicate that there are a variety of differences in maternal handling of infants in these socioeconomic groups.